Modern sintered materials are becoming increasingly important and the properties required of the material demand repeated optimization of what are in many cases contradictory properties, such as hardness and toughness. Since an increase in hardness can generally be obtained in metallic materials, composite materials and pseudo alloys by reducing the grain size, there is a marked trend in the technology of materials to produce ever finer grained types of materials.
The literature gives examples of processes, in particular for the production of contact materials (e.g. H. Schreiner, "Pulvermetallurgie elektrischer Kontakte", publishers Springer-Verlag Berlin, Gottigen, Heidelberg 1964) in which composite materials (e.g. AgNi, AgCdO) may first be obtained as sparingly soluble compounds by conventional chemical precipitation from salt solutions and these sparingly soluble compounds may be decomposed by a subsequent heat treatment and finally reduced to metal mixed powders.
Composite alloy powders consisting of tungsten metal particles with a thin shell of metals of the iron group elements are described in European 98,944.
These tungsten alloy powders which are capable of being sintered are produced by a special method of spray drying with simultaneous reduction by hydrogen at a temperature of at least 800.degree. C., the starting materials consisting entirely of soluble compounds of the alloying elements. This process is therefore not universally applicable and disproportionately expensive on account of the large amount of energy required for the reaction spray drying. Moreover, reduction of the agglomerated oxides under free fall according to European 98,944 is difficult to control by means of the apparatus employed and requires great technical expenditure and high operating costs.
It was therefore an object of the present invention to provide metal powder agglomerates which do not have the disadvantages described above. The metal powder agglomerates according to the present invention fulfil these requirements.